1. Field of the Invention
The invention relates generally to a method and a device for filtering out baseline fluctuations from an electrocardiogram by means of a high pass or band pass filter.
2. Description of the Related Art
Electrocardiograms derived from patients are normally overlaid by disturbance signals such as, for example, the 50 Hz (60 Hz in the United States) alternating voltage induced by the alternating current grid, electrical muscle potentials and artifacts resulting from taking the electrocardiogram from the patient. To the extent that these disturbances are of low-frequency type in comparison with the heartbeat rate, they are expressed in the form of baseline fluctuations in the respectively recorded electrocardiogram.
It is known for example from "Journal of Clinical Engineering", Volume 7, No. 3, July-September 1982, pages 235-240, to filter out these baseline fluctuations from the recorded electrocardiogram by means of a high pass filter. In this case, the lower cut off frequency of the high pass filter is set to a value which is below the frequencies which are characteristic of the heart signals at the lowest occurring heart rate. At high heartbeat rates, there is therefore a disturbance frequency range which is not covered by the high pass filtering.